Question

The maximum electron density in the ionosphere in the morning is ${10}^{10}{m}^{-3}$. At noon time, it increases to $2\times {10}^{10}{m}^{-3}$. Find the ratio of critical frequency at noon and the critical frequency in the morning.

• A. 2
• B. 2.82
• C. 4
• D. 1.414

Answer 1

Answer: (D)

1.414

Given, the maximum electron density in the morning
$N_{max}={10}^{10}{m}^{-3}$
$f_c^{\prime }=9(N_{max}{)}^{1/2}$
$=9({10}^{10}{)}^{1/2}$
Critical frequency $f_c^{\prime }=9\times (N_{max}^{\prime }{)}^{1/2}$
$=9\times (2\times {10}^{10}{)}^{1/2}$
$=9\times \sqrt{2}\times {10}^5$
the ratio of critical frequency at noon and critical frequency in the morning.
$\frac{f{"}_c}{f_c^{\prime }}=\frac{9\times \sqrt{2}\times {10}^5}{9\times {10}^5}$
or $\frac{f{"}_c}{f_c^{\prime }}=\sqrt{2}=1.414$